Determination of Therapeutic g-Aminobutyric Acid Analogs in Forensic Whole Blood by Hydrophilic Interaction Liquid Chromatography–Electrospray Tandem Mass Spectrometry

Vigabatrin, pregabalin, gabapentin and baclofen are g-aminobutyric acid analogs that are used in the treatment of epileptic seizures (vig-abatrin, pregabalin and gabapentin) and spasticity (baclofen). The intake of these drugs may induce adverse reactions and impair the ability of an individual to drive a vehicle. There have also been reports of cases of intoxication and fatalities from overdoses. For rapid and accurate quantification of these drugs in forensic cases, an ultraper-formance liquid chromatography tandem mass spectrometry method using pneumatically assisted electrospray ionization has been devel-oped. The technique has been validated on both ante- and post-mortem human whole blood. The protein in the blood samples was removed by the addition of a mixture of methanol and acetonitrile, and the extract was ultrafiltered and diluted with acetonitrile. The separation was performed by hydrophilic interaction liquid chroma-tography. Calibration of the system was achieved through use of ma-trix-matched calibrants combined with isotope dilution. The lower limits of quantification were 0.02–0.04 mg/L, and the relative intra-laboratory reproducibility standard deviations were <4 and 8 % at concentrations of 10 and 1 mg/L, respectively. The mean true recov-eries were>89%. The trueness expressed as the relative bias of the test results was within +7 % at concentrations of 1–40 mg/L for vig-abatrin, pregabalin and gabapentin and of 0.1–4 mg/L for baclofen